A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

The electrician, who is fully booked up today, tried for several hours
yesterday to pinpoint the cause and thought he had found it. But then
the "fuse" (i.e. switch) popped out again later in the afternoon.

Does anyone have any comments as to the cause? And how would an
electrician go about narrowing down the problem area? According to my
relative, the electrician knows what he's doing, i.e. isn't an
amateur.

How does one trace through all the wiring in the affected side,
especially given the age of the property?

Thanks.

MM

On Thursday, 25 July 2019 07:29:51 UTC+1, MM wrote:

A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

The electrician, who is fully booked up today, tried for several hours
yesterday to pinpoint the cause and thought he had found it. But then
the "fuse" (i.e. switch) popped out again later in the afternoon.

Does anyone have any comments as to the cause? And how would an
electrician go about narrowing down the problem area? According to my
relative, the electrician knows what he's doing, i.e. isn't an
amateur.

How does one trace through all the wiring in the affected side,
especially given the age of the property?

Thanks.

MM

Half the house without power means a whole CU dead, not one final circuit. They're called MCBs btw. If any one MCB tripped you'd only lose one circuit.. You're presumably losing the whole CU, so it sounds like it has an RCD that's tripping. If that's the case, there are 2 tests to do. Insulation test each final circuit, then PAT test or insulation test all your appliances. Usually that will pinpoint the culprit.

Sometimes you can find the bad appliance by just insulation testing with a multimeter, one probe on L&N & the other on E plug pin - with the appliance unplugged of course. There should be no conduction there. So you may solve it with a £10 multimeter and an hour. Sometimes the fault is only picked up with high voltage testing.

A clear pic of the 'fusebox' would help


NT

On Wed, 24 Jul 2019 23:45:14 -0700 (PDT), wrote:

On Thursday, 25 July 2019 07:29:51 UTC+1, MM wrote:

A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

The electrician, who is fully booked up today, tried for several hours
yesterday to pinpoint the cause and thought he had found it. But then
the "fuse" (i.e. switch) popped out again later in the afternoon.

Does anyone have any comments as to the cause? And how would an
electrician go about narrowing down the problem area? According to my
relative, the electrician knows what he's doing, i.e. isn't an
amateur.

How does one trace through all the wiring in the affected side,
especially given the age of the property?

Thanks.

MM

Half the house without power means a whole CU dead, not one final circuit. They're called MCBs btw. If any one MCB tripped you'd only lose one circuit. You're presumably losing the whole CU, so it sounds like it has an RCD that's tripping. If that's the case, there are 2 tests to do. Insulation test each final circuit, then PAT test or insulation test all your appliances. Usually that will pinpoint the culprit.

Sometimes you can find the bad appliance by just insulation testing with a multimeter, one probe on L&N & the other on E plug pin - with the appliance unplugged of course. There should be no conduction there. So you may solve it with a £10 multimeter and an hour. Sometimes the fault is only picked up with high voltage testing.

A clear pic of the 'fusebox' would help

Thanks. I'll take a photo tomorrow. Maybe the electrician will be able
to squeeze him in again today, although yesterday the news was that
he's fully booked up today.

My own house is only 15 years old and, of course, has up-to-date
electrical equipment that one should expect in a 2004 build. My CU, in
the garage, has about 6 smaller MCBs and one larger MCB in the middle.
I rarely get any outage, although the MCBs are all super-sensitive. To
the point where when I was still using filament lamps, just the bulb
blowing would invariably trip the MCB for the relevant lighting
circut.

I gather from what I've been told that the electrical system in the
old house is quite ancient, as the electrican stated that after the
immediate fault has been rectified, at least temporarily, the whole CU
urgently requires replacing. Maybe the wiring, too, which would be an
enormous (and costly) job. It's a large house!

MM

On 25/07/19 07:45, wrote:
On Thursday, 25 July 2019 07:29:51 UTC+1, MM wrote:

A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

The electrician, who is fully booked up today, tried for several hours
yesterday to pinpoint the cause and thought he had found it. But then
the "fuse" (i.e. switch) popped out again later in the afternoon.

Does anyone have any comments as to the cause? And how would an
electrician go about narrowing down the problem area? According to my
relative, the electrician knows what he's doing, i.e. isn't an
amateur.

How does one trace through all the wiring in the affected side,
especially given the age of the property?

Thanks.

MM

Half the house without power means a whole CU dead, not one final circuit. They're called MCBs btw. If any one MCB tripped you'd only lose one circuit. You're presumably losing the whole CU, so it sounds like it has an RCD that's tripping. If that's the case, there are 2 tests to do. Insulation test each final circuit, then PAT test or insulation test all your appliances. Usually that will pinpoint the culprit.

Sometimes you can find the bad appliance by just insulation testing with a multimeter, one probe on L&N & the other on E plug pin - with the appliance unplugged of course. There should be no conduction there. So you may solve it with a £10 multimeter and an hour. Sometimes the fault is only picked up with high voltage testing.

A clear pic of the 'fusebox' would help


NT

If an RCD is tripping then the simplest thing to do is switch off all
the MCBs, reset the RCD, then switch on each MCB in turn until the RCD
trips again. Then you know which circuit is faulty. It can be turned off
and left off until the electrician appears. The other MCBs can be left
on so at least some of the house had power of some sort.

However, if it's an intermittent fault, and the faulty MCB is already
known ("But then the "fuse" (i.e. switch) popped out again later in the
afternoon."), why wasn't that just left off and the RCD reset until the
electrician was able to do further testing?

--

Jeff

The thing is I'd have thought the first thing he'd do is unplug or unwire or
switch off everything on the circuit. Then see what happens. If lucky it
will work, if not then you have probably cleared most of the devices. Then
the slog starts. If its been hot where the property is that might have a
role to play if its an appliance like a fridge or are conditioning unit.
I hate those things. Shortly after moving here we had something similar and
that turned out to be somewhere in the loft between the main wiring and a
ceiling light and its switch. It had perished, very old rubber covered wire.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
wrote in message
...
On Thursday, 25 July 2019 07:29:51 UTC+1, MM wrote:

A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

The electrician, who is fully booked up today, tried for several hours
yesterday to pinpoint the cause and thought he had found it. But then
the "fuse" (i.e. switch) popped out again later in the afternoon.

Does anyone have any comments as to the cause? And how would an
electrician go about narrowing down the problem area? According to my
relative, the electrician knows what he's doing, i.e. isn't an
amateur.

How does one trace through all the wiring in the affected side,
especially given the age of the property?

Thanks.

MM

Half the house without power means a whole CU dead, not one final circuit.
They're called MCBs btw. If any one MCB tripped you'd only lose one circuit.
You're presumably losing the whole CU, so it sounds like it has an RCD
that's tripping. If that's the case, there are 2 tests to do. Insulation
test each final circuit, then PAT test or insulation test all your
appliances. Usually that will pinpoint the culprit.

Sometimes you can find the bad appliance by just insulation testing with a
multimeter, one probe on L&N & the other on E plug pin - with the appliance
unplugged of course. There should be no conduction there. So you may solve
it with a £10 multimeter and an hour. Sometimes the fault is only picked up
with high voltage testing.

A clear pic of the 'fusebox' would help


NT

On Wed, 24 Jul 2019 23:45:14 -0700 (PDT), wrote:

You're presumably losing the whole CU, so it sounds like it has an RCD
that's tripping. If that's the case, there are 2 tests to do.
Insulation test each final circuit, then PAT test or insulation test all
your appliances. Usually that will pinpoint the culprit.

Requires a PAT or insulation tester. A multimeter is only going to
find a gross short not the leakage that may be causing an RCD to trip
assuming that is what is tripping, more info needed.

Assuming it is an RCD were any water heating appliances (kettle,
washing machince, dishwasher, WHY) in use when the afternoon trip
occured? If the the chances are the weater heating element of that
appliance has failed.

An insulation test might not find that as the heating element won't
be switched on. Does an insulation test do L-N, L-E and N-E? Only the
last will find a leaky element and only then if the heater isn't
double pole switched (unlikely).

--
Cheers
Dave.

Jeff Layman formulated on Thursday :
If an RCD is tripping then the simplest thing to do is switch off all the
MCBs, reset the RCD, then switch on each MCB in turn until the RCD trips
again. Then you know which circuit is faulty.

50/50 chance at best - it might be an N to E fault.

On 25/07/2019 07:30, MM wrote:
A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

That leaves a lot of room for speculation untrammelled by facts

As already noted, pictures might help - ideally of both fuse boxes and
of where the cable comes into the house. It might also help to know if
the supply to the house is from overhead cables.




--
Robin
reply-to address is (intended to be) valid

On 25/07/2019 08:52, Jeff Layman wrote:
On 25/07/19 07:45, wrote:
On Thursday, 25 July 2019 07:29:51 UTC+1, MMÂ* wrote:

A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

The electrician, who is fully booked up today, tried for several hours
yesterday to pinpoint the cause and thought he had found it. But then
the "fuse" (i.e. switch) popped out again later in the afternoon.

Does anyone have any comments as to the cause? And how would an
electrician go about narrowing down the problem area? According to my
relative, the electrician knows what he's doing, i.e. isn't an
amateur.

How does one trace through all the wiring in the affected side,
especially given the age of the property?

Thanks.

MM

Half the house without power means a whole CU dead, not one final
circuit. They're called MCBs btw. If any one MCB tripped you'd only
lose one circuit. You're presumably losing the whole CU, so it sounds
like it has an RCD that's tripping. If that's the case, there are 2
tests to do. Insulation test each final circuit, then PAT test or
insulation test all your appliances. Usually that will pinpoint the
culprit.

Sometimes you can find the bad appliance by just insulation testing
with a multimeter, one probe on L&N & the other on E plug pin - with
the appliance unplugged of course. There should be no conduction
there. So you may solve it with a £10 multimeter and an hour.
Sometimes the fault is only picked up with high voltage testing.

A clear pic of the 'fusebox' would help


NT

If an RCD is tripping then the simplest thing to do is switch off all
the MCBs, reset the RCD, then switch on each MCB in turn until the RCD
trips again. Then you know which circuit is faulty. It can be turned off
and left off until the electrician appears. The other MCBs can be left
on so at least some of the house had power of some sort.

However, if it's an intermittent fault, and the faulty MCB is already
known ("But then the "fuse" (i.e. switch) popped out again later in the
afternoon."), why wasn't that just left off and the RCD reset until the
electrician was able to do further testing?

I was going to say both those things too!

On 25/07/2019 08:43, MM wrote:
snip

I gather from what I've been told that the electrical system in the
old house is quite ancient, as the electrican stated that after the
immediate fault has been rectified, at least temporarily, the whole CU
urgently requires replacing. Maybe the wiring, too, which would be an
enormous (and costly) job. It's a large house!

MM


The only thing to look out for (initially) is the presence
of rubber coated wiring or those sockets with round pins
(except for diddy little lighting ones).

If the cables going into the sockets and lighting roses
looks like pvc cable then an urgent isolate and rewire is
not needed, IMHO. Sparkys OTOH just love to frighten and
bull**** clueless owners into expensive rewiring.

On 25/07/2019 10:05, Robin wrote:
On 25/07/2019 07:30, MM wrote:
A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

That leaves a lot of room for speculation untrammelled by facts

As already noted, pictures might help - ideally of both fuse boxes and
of where the cable comes into the house.Â* It might also help to know if
the supply to the house is from overhead cables.





Or even it it used to two houses, now combined but still with two
incomers, main fuses and CU's *(like my bro & SIL's house).

On Thu, 25 Jul 2019 11:40:58 +0100, Andrew
wrote:

On 25/07/2019 10:05, Robin wrote:
On 25/07/2019 07:30, MM wrote:
A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

That leaves a lot of room for speculation untrammelled by facts

As already noted, pictures might help - ideally of both fuse boxes and
of where the cable comes into the house.* It might also help to know if
the supply to the house is from overhead cables.





Or even it it used to two houses, now combined but still with two
incomers, main fuses and CU's *(like my bro & SIL's house).

Yes, I did gather from speaking with my relative that the side of the
house that is unaffected has a separate consumer unit.

MM

On 25/07/2019 08:52, Jeff Layman wrote:
On 25/07/19 07:45, wrote:
On Thursday, 25 July 2019 07:29:51 UTC+1, MMÂ* wrote:

A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

The electrician, who is fully booked up today, tried for several hours
yesterday to pinpoint the cause and thought he had found it. But then
the "fuse" (i.e. switch) popped out again later in the afternoon.

Does anyone have any comments as to the cause? And how would an
electrician go about narrowing down the problem area? According to my
relative, the electrician knows what he's doing, i.e. isn't an
amateur.

How does one trace through all the wiring in the affected side,
especially given the age of the property?

Thanks.

MM

Half the house without power means a whole CU dead, not one final
circuit. They're called MCBs btw. If any one MCB tripped you'd only
lose one circuit. You're presumably losing the whole CU, so it sounds
like it has an RCD that's tripping. If that's the case, there are 2
tests to do. Insulation test each final circuit, then PAT test or
insulation test all your appliances. Usually that will pinpoint the
culprit.

Sometimes you can find the bad appliance by just insulation testing
with a multimeter, one probe on L&N & the other on E plug pin - with
the appliance unplugged of course. There should be no conduction
there. So you may solve it with a £10 multimeter and an hour.
Sometimes the fault is only picked up with high voltage testing.

A clear pic of the 'fusebox' would help


NT

If an RCD is tripping then the simplest thing to do is switch off all
the MCBs, reset the RCD, then switch on each MCB in turn until the RCD
trips again. Then you know which circuit is faulty. It can be turned off
and left off until the electrician appears. The other MCBs can be left
on so at least some of the house had power of some sort.

However, if it's an intermittent fault, and the faulty MCB is already
known ("But then the "fuse" (i.e. switch) popped out again later in the
afternoon."), why wasn't that just left off and the RCD reset until the
electrician was able to do further testing?


Bugger. I was hoping that the OP had passed away.

--
Adam

On Thursday, 25 July 2019 08:42:51 UTC+1, MM wrote:
On Wed, 24 Jul 2019 23:45:14 -0700 (PDT), tabbypurr wrote:
On Thursday, 25 July 2019 07:29:51 UTC+1, MM wrote:

A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

The electrician, who is fully booked up today, tried for several hours
yesterday to pinpoint the cause and thought he had found it. But then
the "fuse" (i.e. switch) popped out again later in the afternoon.

Does anyone have any comments as to the cause? And how would an
electrician go about narrowing down the problem area? According to my
relative, the electrician knows what he's doing, i.e. isn't an
amateur.

How does one trace through all the wiring in the affected side,
especially given the age of the property?

Thanks.

MM

Half the house without power means a whole CU dead, not one final circuit. They're called MCBs btw. If any one MCB tripped you'd only lose one circuit. You're presumably losing the whole CU, so it sounds like it has an RCD that's tripping. If that's the case, there are 2 tests to do. Insulation test each final circuit, then PAT test or insulation test all your appliances. Usually that will pinpoint the culprit.

Sometimes you can find the bad appliance by just insulation testing with a multimeter, one probe on L&N & the other on E plug pin - with the appliance unplugged of course. There should be no conduction there. So you may solve it with a £10 multimeter and an hour. Sometimes the fault is only picked up with high voltage testing.

A clear pic of the 'fusebox' would help

Thanks. I'll take a photo tomorrow. Maybe the electrician will be able
to squeeze him in again today, although yesterday the news was that
he's fully booked up today.

My own house is only 15 years old and, of course, has up-to-date
electrical equipment that one should expect in a 2004 build. My CU, in
the garage, has about 6 smaller MCBs and one larger MCB in the middle.

I suspect the larger one says RCD on it, and is therefore not an MCB. Photo should tell.

I rarely get any outage, although the MCBs are all super-sensitive. To
the point where when I was still using filament lamps, just the bulb
blowing would invariably trip the MCB for the relevant lighting
circut.

I gather from what I've been told that the electrical system in the
old house is quite ancient, as the electrican stated that after the
immediate fault has been rectified, at least temporarily, the whole CU
urgently requires replacing. Maybe the wiring, too, which would be an
enormous (and costly) job. It's a large house!

MM

Funny how peple always seem to recommend you give them money. We await the pics.


NT

Yes when something triggered similar problems here back in the 60s, it was
merely old perished wiring over the ceiling of a bedroom. the rubber had
fallen off and there was a short. We had the house rewired.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"MM" wrote in message
...
On Thu, 25 Jul 2019 11:40:58 +0100, Andrew
wrote:

On 25/07/2019 10:05, Robin wrote:
On 25/07/2019 07:30, MM wrote:
A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

That leaves a lot of room for speculation untrammelled by facts

As already noted, pictures might help - ideally of both fuse boxes and
of where the cable comes into the house. It might also help to know if
the supply to the house is from overhead cables.





Or even it it used to two houses, now combined but still with two
incomers, main fuses and CU's *(like my bro & SIL's house).

Yes, I did gather from speaking with my relative that the side of the
house that is unaffected has a separate consumer unit.

MM

On 25/07/2019 12:54, MM wrote:
On Thu, 25 Jul 2019 11:40:58 +0100, Andrew
wrote:

On 25/07/2019 10:05, Robin wrote:
On 25/07/2019 07:30, MM wrote:
A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

That leaves a lot of room for speculation untrammelled by facts

As already noted, pictures might help - ideally of both fuse boxes and
of where the cable comes into the house.Â* It might also help to know if
the supply to the house is from overhead cables.





Or even it it used to two houses, now combined but still with two
incomers, main fuses and CU's *(like my bro & SIL's house).

Yes, I did gather from speaking with my relative that the side of the
house that is unaffected has a separate consumer unit.

MM


If there are two separate incomers (?originally 2 houses) then if they
are on separate phases, be careful if they resort to running long
extension leads from the unaffected half into the 'dead' half, because
of the voltage difference.

On Friday, 26 July 2019 12:27:41 UTC+1, Andrew wrote:

If there are two separate incomers (?originally 2 houses) then if they
are on separate phases, be careful if they resort to running long
extension leads from the unaffected half into the 'dead' half, because
of the voltage difference.

Some houses use three-phase power. Nobody seems to worry about that.
Does anyone take special precautions when using a UPS whose output
phase may be random relative to other unprotected mains circuits nearby?

John

On 25/07/2019 23:07, wrote:
On Thursday, 25 July 2019 08:42:51 UTC+1, MM wrote:
On Wed, 24 Jul 2019 23:45:14 -0700 (PDT), tabbypurr wrote:
On Thursday, 25 July 2019 07:29:51 UTC+1, MM wrote:

A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

The electrician, who is fully booked up today, tried for several hours
yesterday to pinpoint the cause and thought he had found it. But then
the "fuse" (i.e. switch) popped out again later in the afternoon.

Does anyone have any comments as to the cause? And how would an
electrician go about narrowing down the problem area? According to my
relative, the electrician knows what he's doing, i.e. isn't an
amateur.

How does one trace through all the wiring in the affected side,
especially given the age of the property?

Thanks.

MM

Half the house without power means a whole CU dead, not one final circuit. They're called MCBs btw. If any one MCB tripped you'd only lose one circuit. You're presumably losing the whole CU, so it sounds like it has an RCD that's tripping. If that's the case, there are 2 tests to do. Insulation test each final circuit, then PAT test or insulation test all your appliances. Usually that will pinpoint the culprit.

Sometimes you can find the bad appliance by just insulation testing with a multimeter, one probe on L&N & the other on E plug pin - with the appliance unplugged of course. There should be no conduction there. So you may solve it with a £10 multimeter and an hour. Sometimes the fault is only picked up with high voltage testing.

A clear pic of the 'fusebox' would help

Thanks. I'll take a photo tomorrow. Maybe the electrician will be able
to squeeze him in again today, although yesterday the news was that
he's fully booked up today.

My own house is only 15 years old and, of course, has up-to-date
electrical equipment that one should expect in a 2004 build. My CU, in
the garage, has about 6 smaller MCBs and one larger MCB in the middle.

I suspect the larger one says RCD on it, and is therefore not an MCB. Photo should tell.

I rarely get any outage, although the MCBs are all super-sensitive. To
the point where when I was still using filament lamps, just the bulb
blowing would invariably trip the MCB for the relevant lighting
circut.

I gather from what I've been told that the electrical system in the
old house is quite ancient, as the electrican stated that after the
immediate fault has been rectified, at least temporarily, the whole CU
urgently requires replacing. Maybe the wiring, too, which would be an
enormous (and costly) job. It's a large house!

MM

Funny how peple always seem to recommend you give them money. We await the pics.


NT

There is a well established procedure for detecting which circuit is
causing an RCD to trip.

Viz with the RCD off switch off all mcb's.
Reset the RCD
Turn on each mcb in sequence to determine which circuit is causing the
RCD to trip.
Once identified investigate the 'faulty' circuit for line and neutral to
earth continuity and if necessary check insulation resistance.
Visual checks at accessories may then be required to establish wiring
condition.

Tufnell Park wrote:

There is a well established procedure for detecting which circuit is
causing an RCD to trip.

Viz with the RCD off switch off all mcb's.
Reset the RCD
Turn on each mcb in sequence to determine which circuit is causing the
RCD to trip.

Or if you're unlucky you find it's several of them together, or it's
intermittent.

On Saturday, 27 July 2019 14:45:57 UTC+1, Andy Burns wrote:
Tufnell Park wrote:

There is a well established procedure for detecting which circuit is
causing an RCD to trip.

Viz with the RCD off switch off all mcb's.
Reset the RCD
Turn on each mcb in sequence to determine which circuit is causing the
RCD to trip.

Or if you're unlucky you find it's several of them together, or it's
intermittent.

Yes. That may catch it though, and it takes no real work, learning or equipment.


NT

On 27/07/2019 14:45, Andy Burns wrote:
Tufnell Park wrote:

There is a well established procedure for detecting which circuit is
causing an RCD to trip.

Viz with the RCD off switch off all mcb's.
Reset the RCD
Turn on each mcb in sequence to determine which circuit is causing the
RCD to trip.

Or if you're unlucky you find it's several of them together, or it's
intermittent.

That's only if you are unlucky, most of the time it works!

On Thu, 25 Jul 2019 15:07:46 -0700 (PDT), wrote:

[snip]

Funny how peple always seem to recommend you give them money. We await the pics.

Right-o, I'm back from visiting and here is the pic of said consumer
unit:

http://www.littletyke.myzen.co.uk/sc-consumer-unit.jpg

This was installed in 1996.

Meanwhile, the electrician found the fault. It was burnt insulation on
the cables to the halogen ceiling light in the upstairs bathroom which
caused the wires to short.

Thanks all for the handy tips!

MM

On Fri, 26 Jul 2019 12:26:54 +0100, Andrew
wrote:

On 25/07/2019 12:54, MM wrote:
On Thu, 25 Jul 2019 11:40:58 +0100, Andrew
wrote:

On 25/07/2019 10:05, Robin wrote:
On 25/07/2019 07:30, MM wrote:
A relative lives in a 300-year-old house. Yesterday he called to warn
that when I visit tomorrow (Friday) it's likely that roughly half the
house will still be without power. The other, smaller, half is
unaffected.

The electrician he called has so far not been able to diagnose the
cause of the problem. The half that is out is on a separate "fuse"
box. The other half of the house is unaffected. I write "fuse" in
quotes, but I understand that it does at least have the switches, not
old-fashioned fuse-wire fuses, although the equipment seems to be very
old.

That leaves a lot of room for speculation untrammelled by facts

As already noted, pictures might help - ideally of both fuse boxes and
of where the cable comes into the house.* It might also help to know if
the supply to the house is from overhead cables.





Or even it it used to two houses, now combined but still with two
incomers, main fuses and CU's *(like my bro & SIL's house).

Yes, I did gather from speaking with my relative that the side of the
house that is unaffected has a separate consumer unit.

MM


If there are two separate incomers (?originally 2 houses) then if they
are on separate phases, be careful if they resort to running long
extension leads from the unaffected half into the 'dead' half, because
of the voltage difference.

Actually, my relative *did* run a temporary extension lead to the
kitchen fridge. The freezer in the garage was unaffected. For a pic of
the consumer unit, see he

http://www.littletyke.myzen.co.uk/sc-consumer-unit.jpg

The CU was installed in 1996. Relative will have it replaced asap.
Maybe (some of) the house wiring, too. It'll be a massive job, because
the house was originally built 300 years ago and is huge.

MM

On Fri, 26 Jul 2019 15:21:32 -0700 (PDT), wrote:

On Friday, 26 July 2019 12:27:41 UTC+1, Andrew wrote:

If there are two separate incomers (?originally 2 houses) then if they
are on separate phases, be careful if they resort to running long
extension leads from the unaffected half into the 'dead' half, because
of the voltage difference.

Some houses use three-phase power. Nobody seems to worry about that.
Does anyone take special precautions when using a UPS whose output
phase may be random relative to other unprotected mains circuits nearby?

This is a new one for me. *I* have two UPSs, one for each PC. They are
both by APC. I just plug 'em into the mains.

MM

On Monday, 29 July 2019 16:58:34 UTC+1, MM wrote:
On Thu, 25 Jul 2019 15:07:46 -0700 (PDT), tabbypurr wrote:

[snip]

Funny how peple always seem to recommend you give them money. We await the pics.

Right-o, I'm back from visiting and here is the pic of said consumer
unit:

http://www.littletyke.myzen.co.uk/sc-consumer-unit.jpg

This was installed in 1996.

Meanwhile, the electrician found the fault. It was burnt insulation on
the cables to the halogen ceiling light in the upstairs bathroom which
caused the wires to short.

Thanks all for the handy tips!

MM

Very blurry. Looks like you have no RCD there.


NT

On Monday, 29 July 2019 17:06:34 UTC+1, MM wrote:
On Fri, 26 Jul 2019 15:21:32 -0700 (PDT), wrote:

On Friday, 26 July 2019 12:27:41 UTC+1, Andrew wrote:

If there are two separate incomers (?originally 2 houses) then if they
are on separate phases, be careful if they resort to running long
extension leads from the unaffected half into the 'dead' half, because
of the voltage difference.

Some houses use three-phase power. Nobody seems to worry about that.
Does anyone take special precautions when using a UPS whose output
phase may be random relative to other unprotected mains circuits nearby?

This is a new one for me. *I* have two UPSs, one for each PC. They are
both by APC. I just plug 'em into the mains.

MM

Just like everyone else does. However, if the mains fails the two UPSs
will be outputting asynchronously generated waveforms, so some of the
time the outputs will almost certainly be out of phase with each other
and the relative peak voltages will be even higher than with two phases
from a three-phase mains supply.
In other words, your situation with two UPSs is potentially more
"dangerous" than running an extension lead from one phase of a
three-phase mains supply to an area with a different phase.

In reality, there is no problem, just as there is no problem with
having different phases of a three-phase supply near each other.
This is because each live connection is insulated and to suffer
the effects of the higher voltage difference there would have to be
multiple simultaneous insulation failures.

(I know that three phase mains will deliver much higher fault
currents in a phase to phase fault than UPSs, but for that to happen
there still need to be multiple simultaneous insulation failures.)

John